P2002: DPF efficiency below threshold
P2002 means the engine computer thinks the particulate filter is no longer trapping soot the way it should. It is the code most often misread as "replace the DPF". What it really measures, and what usually sits behind it.
- Urgency
- Soon
- Reads the vehicle
- Your workshop
- Measures the filter
- Us
- Clean from
- ₹6,500
In plain words
P2002 is the generic code for "Diesel Particulate Filter Efficiency Below Threshold, Bank 1" (P2003 is the same thing on a second bank). The engine computer judges efficiency from the pressure drop across the filter, sometimes combined with temperature and soot-model data. If the filter is holding less back pressure than a working filter should, the logic concludes that soot is passing straight through it.
The important word is "concludes". The computer cannot see the filter; it infers its state from a pressure sensor and two small pipes. A genuinely failed substrate, cracked or melted, will set this code. So will a split pressure line, a drifted sensor, a filter that has been through an uncontrolled regeneration, or a filter that was removed and gutted by a previous owner. Of these, the physically failed filter is the least common.
Usual causes, most common first
- 01A cracked, melted or collapsed substrate after an uncontrolled regeneration, usually on a filter that was already ash-loaded
- 02A split, blocked or disconnected differential pressure line, so the sensor reads a false low pressure drop
- 03A drifted or failed differential pressure sensor
- 04A filter that has been hollowed out or replaced with a straight pipe by a previous workshop
- 05Less often, a filter so blocked on one side that the sensor reads it as bypassed
In this order
Cheapest and least invasive first. Each step rules something out before you spend on the next.
Before anyone quotes for a replacement filter, have your workshop inspect the two differential pressure lines and the sensor. This is the cheapest cause and a frequent one.
Have the live differential pressure read at idle and under load, and compare it with the expected range for the vehicle. A reading near zero under load points at the lines or sensor, or at a gutted filter.
If the lines and sensor are good, have the filter removed and sent to us. The flow test tells you in minutes whether the substrate is intact.
If the substrate is damaged, the filter is replaced, and the cause of the overheating that damaged it, usually ash loading and repeated forced regenerations, needs addressing on the new one.
What we find when the filter reaches us
Flow and back pressure are measured on arrival, before anything is quoted, and again after cleaning. Both readings go back with the filter.
- A damaged substrate is visible on the bench: flow is far too high for the filter type and the face or core shows cracking. Those are not cleaned, and we say so.
- An intact filter with a good flow reading means the code was a sensor or line fault, and the filter was never the problem. That is a common finding on P2002.
- A filter with very low flow on arrival that recovers after cleaning is the blocked-on-one-side case, and cleaning resolves it.
The symptom checker's view
The same pattern, scored from your answers. Each result links to the service that addresses it.
Asked about this one
Not on its own. P2002 is set whenever the pressure drop across the filter is lower than expected, and a split pressure line or a drifted sensor produces that reading on a perfectly good filter. Only a flow test of the filter itself tells you whether the substrate has failed.
If the substrate is intact, yes, and if it was blocked on one side cleaning resolves the code. If the substrate is cracked or melted, cleaning cannot repair it and we will tell you so before any work is done.
It will clear the lamp until the next drive cycle in which the computer re-runs its efficiency check, and then the code returns. Clearing it without finding the cause only loses the freeze-frame data your workshop needs.
Related problems
All problems and codesSend the code and a photograph
A picture of the scanner screen or the dashboard message, the vehicle and mileage, and how it is behaving. You will get a straight answer on whether the filter is the problem, and what it costs to find out.